Eisenmenger syndrome (or complex)

Children born with Eisenmenger syndrome are born with a hole between the two pumping chambers -- the left and right ventricles -- of the heart (ventricular septal defect). The hole allows blood that has already picked up oxygen from the lungs to flow back into the lungs, instead of going out to the rest of the body. The increased blood flow and high pressure damages the small blood vessels in the lungs.